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Investigating the influence of regional climate and oceanography on marine radiocarbon reservoir ages in southwest New Zealand

Hinojosa, Jessica L. and Moy, Christopher M. and Prior, Christine A. and Eglinton, Timothy I. and McIntyre, Cameron P. and Stirling, Claudine H. and Wilson, Gary S. (2015) Investigating the influence of regional climate and oceanography on marine radiocarbon reservoir ages in southwest New Zealand. Estuarine, Coastal and Shelf Science, 167 . pp. 526-539. ISSN 0272-7714.

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The New Zealand fjords are located at a latitude where distinct oceanic and atmospheric fronts separate carbon reservoirs of varying residence time. The marine radiocarbon reservoir age in this region is likely to deviate from the global average reservoir age over space and time as frontal boundaries migrate north and south. Here we present new estimates of modern radiocarbon reservoir age using the radiocarbon content of bivalve shells collected live before 1950. Multiple measurements from hydrographically distinct sites support the use of a ΔR, defined as the regional offset between measured and modeled marine radiocarbon reservoir age, of 59 ± 35 years for the New Zealand fjords. We also assess the radiocarbon content of bulk surface sediments throughout the fjord region. Sediment with a higher proportion of marine organic carbon has relatively less radiocarbon than more terrestrial sediment, suggesting a short residence time of organic carbon on land before deposition in the fjords. Additionally, we constrain reservoir age variability throughout the Holocene using coeval terrestrial and marine macrofossils. Although our modern results suggest spatial consistency in ΔR throughout the fjords, large deviations from the global average marine radiocarbon reservoir age exist in the paleo record. We find four ancient ΔR values, extending back to ∼10.2 cal kyr BP, to be negative or near zero. A likely cause of younger radiocarbon reservoir ages at select intervals throughout the Holocene is the increased influence of the Southern Hemisphere westerly winds, which cause extreme precipitation in the region that delivers terrestrial carbon, enriched in radiocarbon, to fjord basins. However, bivalve depth habitat may also influence radiocarbon content due to a stratified water column containing distinct carbon pools. This work highlights the need for thorough assessment of local radiocarbon cycling in similar regions of dynamic ocean/atmosphere frontal zones, especially fjords and other semi-restricted estuaries.

Item Type:Article
Related URLs:
URLURL TypeDescription
Hinojosa, Jessica L.0000-0002-8589-102X
Moy, Christopher M.0000-0002-2177-5265
Additional Information:© 2015 Elsevier Ltd. Received 17 April 2015; Received in revised form 27 October 2015; Accepted 2 November 2015; Available online 6 November 2015. Funding for this research was provided by a University of Otago research grant, a Royal Society of New Zealand Marsden Fast-Start grant (#UOO1118), and a GNS Science competitive isotope funding grant to C.M.M. J.L.H. gratefully acknowledges support from a U.S. Department of State Fulbright grant.We thank Robert Van Hale and Dianne Clark (Department of Chemistry, University of Otago) for laboratory and data analysis support; members of the Rafter Radiocarbon Laboratory (GNS Science) for training and laboratory support; members of the ETH Zürich Biogeosciences group for laboratory support and access to resources; and Alan Beu of GNS Science and Bruce Marshall of Te Papa Tongarewa for providing additional bivalve specimens. Data in this paper can be accessed through supporting materials or via contact with corresponding author at
Funding AgencyGrant Number
University of OtagoUNSPECIFIED
Royal Society of New ZealandUOO1118
Fulbright CommissionUNSPECIFIED
Subject Keywords:Radiocarbon dating; Carbon cycle; Fjord dynamics; Water mixing; New Zealand
Record Number:CaltechAUTHORS:20160128-082638212
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Official Citation:Jessica L. Hinojosa, Christopher M. Moy, Christine A. Prior, Timothy I. Eglinton, Cameron P. McIntyre, Claudine H. Stirling, Gary S. Wilson, Investigating the influence of regional climate and oceanography on marine radiocarbon reservoir ages in southwest New Zealand, Estuarine, Coastal and Shelf Science, Volume 167, Part B, 20 December 2015, Pages 526-539, ISSN 0272-7714, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64037
Deposited By: Tony Diaz
Deposited On:28 Jan 2016 17:20
Last Modified:09 Mar 2020 13:19

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